This invention relates to a welding technology giving a chromium oxide passivation treatment at the time of welding and a gas supplying system used at the time of welding.
Heretofore, the chromium oxide passivation treatment been performed on the weld under the condition that chromium is allowed to be diffused by micro-crystallizing a most-outside surface of a piping by means of complexly-electrolytic polishing the weld of austenite system stainless steel (SUS316L), or the chromium oxide passivation treatment been performed after welding had been performed using ferrite system stainless steel excellent in the diffusion of chromium and welding had been completed. Since the chromium oxide passivation treatment is performed after completion of welding in both cases, re-chromium oxide passivation treatment is required when welding of the gas-piping and members on which the chromium oxide passivation treatment has been given is performed, whereby much expense in time and effort have been taken.
Moreover, gases doped with oxygen used for giving the chromium oxide passivation treatment at the time of welding are fed to a point at which welding is performed after oxygen of 100% is correctly controlled by a gas panel on which a fluid control device is equipped, and so a total length of the piping reaches tens of meters. Besides, it has been very hard to use, since it is performed manually also in switching, therefore, problems of improper operations are caused. Moreover, even though a length in the piping to be welded reaches four meters, in addition the space required for welding is very wide, a fluid control device is installed on the panel or the like in an arc gas and back-sealed gas supplying systems of the prior art, whereby handling of a gas supplying has been hard.
The object of the invention makes the treatment possible in a short time and leads to improvement in productivity by giving the chromium oxide passivation treatment in concurrence with welding.
The object of the invention is to provide a gas supplying system capable of supplying oxygen, or moisture, and hydrogen correctly controlled for forming an oxidized passivity film on the weld.
The object of the invention is to solve the problems of the improper operations or the like due to manually switching.
This invention is a welding technology for forming an chromium oxide a passive state on a weld, comprising:
switching gases to be flown into the cavity from an argon gas, or mixed gases of the argon gas and hydrogen gas to the argon gas which is doped with an oxidizing gas; as well as irradiating at least the weld with an extent of arc or an electron beam which does not melt the weld, after welding while flowing argon gas, or mixed gases of the argon gas and hydrogen gas as the back-sealed gas into a cavity of material to be welded which a chromium passivity film is formed on an inner surface of a cavity.
The invention is a gas supplying system supplying a back-sealed gas and an arc gas (gases flowing in a welding head) used at the time of welding wherein a gas flow rate and a gas concentration are correctly controlled by a fluid control device.
The invention is characterized in that a switching valve for the gases at the time of welding and at the time of the chromium oxide passivation treatment can be controlled by a timer, and all components constituting the gas system can be controlled by electric signals (it is preferable that all components used are constituted by metal, moreover, a chromium oxide passivation film is formed on a portion contacting with the gases).